Method of and apparatus for drying



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A F WRIGHT METHOD oF AND APPARATUS FOR DRYING Filed May 20. 192 }\i May 13 1 924.

OOOOO O O O Patented May 13, 1924.

UNITED STATES PATENT OFFICE.

ARCHIBALD F. WRIGHT, OF EAST ORANGE, NEW JERSEY, ASSIG-NOR T'O INDUSTRIAL DRYER CORPORATION, OF NEWARK, NEW JERSEY, A CORPORATION OF NEW JER- SEY.

METHOD OF-AND AIPARATUS FOR DRYING.

Application led May 20,

To all whom t may concern:

Be it known that 1, ARCHIBALD F. WRIGHT, a citizen of the United States, residing at East Orange, county of Essex, and State of New Jersey, have invented a certain new and useful Method of and Apparatus for Drying, of which the following is a specification.

This invention is a method of and apparatus for drying wherein the evaporation of moisture is conducted under such conditions as to reduce the volume of the drying agent, usually atmospheric air, in proportion to the moisture content of the material under t-reatment while at the same time the speed or velocity, and preferably the temperature, of such drying agent are maintained constant, as a result of which treatment there is obtained marked economy in the heat, usually steam, required for the maintenance of the drying agent at the temperature necessary for the evaporation of moisture.

In the drying art, the evaporation of moisture by the ow of heated air into Contact with the moist material results in carrying oit a substantial percentage of the moisture during a period, say one hour which may be considered the first stage oit the treatment, and thereafter the evaporation takes place more slowly during the second period, say the second hour, and as the moisture content of the mass decreases, the evaporation takes place still more slowly during the successive periods and the final period of the treatment. It is usual to circulate air in a given volume per minute, and at a desired velocity and under a certain temperature, during the initial, successive and final periods in the treatment of the material; but as the moisture content of the material decreases in a certain ratio during the successive and nal stages of the treatment. the operation of heating the large volume of air to a predetermined temperature throughout all the stages of the treatment results in a very considerable 'waste and loss of heat energy.

It is the ypurpose of this invention to conserve the energy required for the maintenance of the drying agent at the desired temperature, and at the same time to conduct the treatment with eiciency and with a material saving in the time necessary for 1920. Serial No. 382,838.

the evaporation of moisture from the material.

According to this invention, the volume of air utilized as the drying medium is reduced progressively and in proportion to a decrease in the moisture content of the mass, while at the same time the Velocity of the air, and preferably the temperature thereof, is maintained constant.

In a practical form of apparatus, means are provided for supporting the moist material in separated masses so as to establish flow channels for the circulation of the drying medium, the latter being supplied in the required volume and at the desired velocity by the operation either of a blower or an exhauster, and said dryin medium being initially raised to a desire temperature by conducting the air into contact with an initial heater.

Means are provided for conducting the flow of the drying medium into contact with the masses of moist material the area of which contact is increased in proportion to a reduction in the moisture content of the masses. Said controlling means in the embodiment of the invention comprises dampers positioned in series at the respective ends of the material-supporting means, and said dampers are operable individually and in a manner to vary the o erative length of the channels through w ich the drying medium must flow.

At the initial stage, the air circulating means supplies the air in large volumes, and at proper velocity and at the required temperature, for carrying off a certain percentage of moisture, but as the moisture content decreases in the masses of material, the volume of air is proportionately decreased although the velocity andtemperature of such decreased volume ofair remain constant, and simultaneously therewith the operative length of the air channels are increased, such decrease in the volume of air and the increase in the operative length of the air. channels being effected at successive stages in the treat-ment of the material, and such changes in the air volume and the length of the fiow channels being proportionate to the decrease in the moisture content oi the masses. The variation in the length of the air channels is due to the manipulation of the dampers, which manipulation may be effected manually, whereas the variation in the air volume 1s brought about either by controlling the area of the air inlet to the blower or by varying the speed of said blower, as will be readily understood by those skilled in the art.' i

Other functions and advanta es of the in'- vention will ap ar from the ollowin description taken 1n connection with the rawin ,wherein- 1 re 1 isa vertical longitudinal sectiona view through my apparatus illustrat ing the dampers positione for directing the flow of air durmg an early stage in the evaporation of moisture from the masses of material.

Figure 2 is a similar view of the apparatus with the dampers adjusted to a differ; ent position for controlling the flow of air during an intermediate stage of the treatment and Figure 3 is a similar view of the apparatus with the dampers adjusted for controlling the air flow during the final stage of the evaporation.

Within a casing or housing A are provided a series of baffles Bthe end portions of which terminate adjacent the end walls of the housing, leavin spaces or ilues C D for the circulation o the drying medium usually atmospheric air. The bailles are shown as extending horizontally within"the housing, and they are spaced in parallel or substantially parallel relation to pro uoe iow channels 1, 2, 3, 4, 5, 6, 7, 8,-eight in number,'although the number may be increased or decreased as desired according to the capacity of the machine. Said flow channels accommodate `suitable means 'for supporting moist material' in separated masses within the housing, the material supportin means being in the form of trays, or en less belts or conveyors, or ortabl'e trucks, may be used when and w ere desired.

At or near one end of the housingI i`s a chamber E for the initial heater F, the latter being shown as steam coils, although other air heating means may be substituted for said steam coils.4 Said chamber E communicates by a port e with the first ow channel of the series, said port e being shown as positioned at the bottom of the housing so that the direction of air flow will be from the bottom toward the to of said housing, although the direction o air fiow may be reversed, should occasion require.

Air is circulated through the flow chan- 4nel by a blower or exhauster, a blower Gr bein shown in Figure 1 for this purpose. As 1s usual, theblower is provided with an axial inlet for the air, and it is connected by a wind trunk g with chamber E,

, The housing amena said blower operating to feed air in the required volume and -at the desired velocity.

to said chamber E through which the air fiows so as to have contact with the heater F for initially heating the airto the desired temperature.

A is provided with one or a plurality of outlets-a for the outiiow of air, aden more or less with moisture evaporated from the material under treatment, said outlet being shown as provided with a dam r a.

T e flow of air within the channels is controlled by two series of dampers H I, one series being sitioned within the vertical s ace C an Athe dampers of the other series ying within the other space D. Each dam r is shown as a flat plate, the same being inged in the horizontal plane of one of the bales B. The dampers of the two series are adapted for indivldual operation, and said dampers are movable for closing the spaces C D in a manner to control the operative length of the flow channels.

In operation the material in se arated masses is intro uced into the flow c annels, steam is supplied to the initial heater F, and blower is started for circulating air through the chamber E and within the flow channels. During the initial stage of the evaporation, the material as a rule ives off moisture freely and a relatively arge percentage of the moisture is evaporated rom the material and carried off by the air flowing1 within the channels, for which purpose t e blower is operated to feed air in maximum quantity and at a desired velocity, the air being heated by the coils F to the required temperature. At this sta e in the procedure, the middle damper in the series is closed across the space C and po sitioned in re ister'with the middle bafile B, all the other ampers in the series H andI being opened, as shown in Figure 1, as a result of which damper adjustment the inflowing heated air circulates once through the channels 1, 2, 3, 4, thence into space D, and thence in Van opposite direction within the channels 5, 6, 7, 8, as indicated by the arrows in said Figure 1, the air finding an exity at a from the housing.

Air in the required volume flows through fiues 1, 2, 3, 4, and thence through ues 5, 6, 7, 8, so as to contact twice with the material between the point of inlet and outlet of the housing, the air exchanging heat for moisture and operating to carry off a large percentage of moisture from the material during the first sta e of the treatment, which stage may exten over a period of one hour or more.

A substantial percentage of the moisture having been evaporated and carried off during the first stage and the moisture content of the material having decreased to an apllO llo

preciableextent, the dampers H 1 are adjusted as in Figure 2 and the blower operated to feed air in a reduced volume, although the velocity and temperature of the air remain constant. As shown in said F igure 2, the second and fifth dampers in series H and the second damper in series I are closed so as to rev ister with the second, fourth and sixth b es B, the effect of which is to direct the inowing air through channels 1, 2, back through channels 3, 4, thence through channels 5, 6, and back again through channels 7, 8, thence to the exit a. The dampers when adjusted as in Figure 2 control the flow of air in a manner to prolong the contact of the air with the moist material, the effect of the damper adjustment being to materially increase the operative length of the flow channels as compared with the length of said channels shown in Figure l. As the moisture content of the material during the second stage is decreased to an appreciable extent as compared with the moisture content of said material during the first stage, the fiow of air in reduced volume, although at the initial velocity and at the same temperature, during the second stage is quite sufficient for the purpose of evaporating moisture. The treatment during the second stage is continued for such a period as is or may be required, say for another hour or even longer, during which period the moisture remaining in the material is further reduced until the material attains a condition which requires further treatment in order to evaporate from it that relatively small percentage of moisture, which evaporization haa heretofore required prolonged application of heated air with the purpose in View of ultimately attaining the condition known in the art as bone dry. lt is this final stage in the treatment of the material which hitherto has been most difficult of attainment and which has seriously involved the great loss and waste of the heat energy necessary t0 raise the large volume of air hitherto used to a temperature suitable for carrying further the evaporating process; but the loss of heat incidental to prior evaporating procedures and apparatuses does not apply in my present invention, for the reason that my apparatus and procedure are controlled to attain a prolonged application of the heated air in reduced volume to material containing a relatively small moisture content, the volume of the air supplied at this stage of treatment being decreased proportionately to the reduction in the moisture content of the material, although the velocity and temperature of the air remain constant throughout the final period of treatment.

To attain the prolonged application of the air in reduced volume to material containing a low percentage of moisture, the dampers H I are adjusted as in Figure 3, and concurrently with such damper adjustment the blower is controlled to feed air in a smaller volume, although the air velocity and the air temperature remain constant. As shown in Figure 3, the first, third, fifth and seventh dampers in series H and the". three dampers in series I are closed for re istration with the bafiles B, in order to sustantially increase the operative length of the fiow channel Within the housing; and thus the air flows back and forth successively through the channels l, 2, 3, 4, 5, 6, 7 and 8, whereby the air in reduced volume has prolonged contact with the masses of material, the period of air flow under these conditions being prolonged as desirable or found necessary for the evaporation of that small percentage of moisture which is present in the material after the latter shall have been subjected to treatment during the first and subsequent stages with the apparatus ad- )usted as in Figures l and 2 respectively.

Having thus fully described the invention tft what ll claim as new and desire to secure by Letters Patent is:

1. ln the art of drying, the process which consists in circulating a gaseous dryin medlum in a desired volume and at suitable velocity and at a desired temperature into contact With-moist material for a period of time to evaporate a certain percentage of moisture from such material; and subsequently to such period of treatment, circulating a gaseous drying medium in decreased volume, and at the same velocity and temperature, into contact with the same material, the volume-of the gaseous drying medium being decreased proportionately to a reduction in the moisture content of the material during the subsequent period of treatment.

2. In the art of drying, the process which consists in circulating air in relatively large volume and at a desired velocity and temperature into contact with moist material for a desired period of time for eii'ecting the evaporation of a relatively large percentage of the moisture content of such material; and 115 subsequently to such period of treatment, circulatin air in decreased volume but at substantia ly the same velocity and temperature into contact with the same material for a further period of time to attain a de- 12o sired evaporation of the remainder of the moisture from the material, the decrease in the volume of air being proportionate to a red uftion in the moisture content of the materia 3. lin the art of drying, the process which consists in circulating air in a desired volume and at a desired velocity and temperature throu h flow channels of predetermined lengt and into contact with moist 130 .material for a given eriod of time to attain the evaporation o a certain percento. e of moisture; progressively increasing-t eoperative length of the ow channels during a subsequent sta or stages in the treatment of the materia and concurrently therewith decreasing the volume of air, while maintaining the velocity and temperature con'stant, circulated into contact with such material during the successive stage or stages in the treatment thereof.

4. In the art of drying, the process which consists in circulating air4 into contact with moist material, and progressively decreasing the volume of air so circulated proportionately to a reduction in the moisture content of said material.

5. In a drying apparatus, encasin means provided with a succession of flow c annels, the latter being unobstructed, means for circulatin within said flow channels a drying atmosp ere at constant velocity and temperature and in decreasing volume proportionately to an increase in the operative length of said flow channels, means for effecting a variation in the operative length of said flow channels, and an initial heater constituting the sole means for heating the drying atmosphere.

6. In a drying apparat-us, encasin means provided with a succession of flow c annels, the latter being unobstructed, means for circulatin within said iiow channels a drying atmosp ere at constant velocity and temperature and in decreasing volume proportionately to an increase in the operative length 

